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Ingo Molnar 4e44f3497d sys_time() speedup 
Improve performance of sys_time().  sys_time() returns time in seconds, but
it does so by calling do_gettimeofday() and then returning the tv_sec
portion of the GTOD time.  But the data structure "xtime", which is updated
by every timer/scheduler tick, already offers HZ granularity time.

The patch improves the sysbench OLTP macrobenchmark significantly:

2.6.22-rc6:

#threads
   1:        transactions:                        3733   (373.21 per sec.)
   2:        transactions:                        6676   (667.46 per sec.)
   3:        transactions:                        6957   (695.50 per sec.)
   4:        transactions:                        7055   (705.48 per sec.)
   5:        transactions:                        6596   (659.33 per sec.)

2.6.22-rc6 + sys_time.patch:

   1:        transactions:                        4005   (400.47 per sec.)
   2:        transactions:                        7379   (737.77 per sec.)
   3:        transactions:                        7347   (734.49 per sec.)
   4:        transactions:                        7468   (746.65 per sec.)
   5:        transactions:                        7428   (742.47 per sec.)

Mixed API uses of gettimeofday() and time() are guaranteed to be coherent
via the use of a at-most-once-per-second slowpath that updates xtime.

[akpm@linux-foundation.org: build fixes]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-16 09:05:48 -07:00
..
irq Improve behaviour of spurious IRQ detect 2007-07-16 09:05:46 -07:00
power PM: introduce set_target method in pm_ops 2007-07-01 12:29:44 -07:00
time Remove capability.h from mm.h 2007-07-16 09:05:45 -07:00
.gitignore
acct.c [PATCH] kernel: change uses of f_{dentry, vfsmnt} to use f_path 2006-12-08 08:28:42 -08:00
audit.c Audit: add TTY input auditing 2007-07-16 09:05:47 -07:00
audit.h Audit: add TTY input auditing 2007-07-16 09:05:47 -07:00
auditfilter.c audit: fix oops removing watch if audit disabled 2007-06-24 08:59:12 -07:00
auditsc.c kerneldoc fix in audit_core_dumps 2007-07-16 09:05:48 -07:00
capability.c [PATCH] pid: replace do/while_each_task_pid with do/while_each_pid_task 2007-02-12 09:48:32 -08:00
compat.c signal/timer/event: timerfd compat code 2007-05-11 08:29:36 -07:00
configs.c use simple_read_from_buffer in kernel/ 2007-05-09 12:30:49 -07:00
cpu.c microcode: use suspend-related CPU hotplug notifications 2007-05-09 12:30:56 -07:00
cpuset.c Reduce cpuset.c write_lock_irq() to read_lock() 2007-07-16 09:05:43 -07:00
delayacct.c sched: update delay-accounting to use CFS's precise stats 2007-07-09 18:52:00 +02:00
die_notifier.c move die notifier handling to common code 2007-05-08 11:15:04 -07:00
dma.c [PATCH] struct seq_operations and struct file_operations constification 2006-12-07 08:39:46 -08:00
exec_domain.c Remove obsolete #include <linux/config.h> 2006-06-30 19:25:36 +02:00
exit.c Audit: add TTY input auditing 2007-07-16 09:05:47 -07:00
extable.c
fork.c user namespace: add unshare 2007-07-16 09:05:47 -07:00
futex.c FUTEX: Restore the dropped ERSCH fix 2007-06-24 12:08:53 -07:00
futex_compat.c Revert "futex_requeue_pi optimization" 2007-06-18 09:48:41 -07:00
hrtimer.c Add suspend-related notifications for CPU hotplug 2007-05-09 12:30:56 -07:00
itimer.c The scheduled -EINVAL for invalid timevals in setitimer 2007-05-08 11:15:13 -07:00
kallsyms.c fix possible null ptr deref in kallsyms_lookup 2007-05-30 10:51:38 -07:00
Kconfig.hz [PATCH] HZ: 300Hz support 2006-12-07 08:39:36 -08:00
Kconfig.preempt Fix trivial typos in Kconfig* files 2007-05-09 07:12:20 +02:00
kexec.c kdump/kexec: calculate note size at compile time 2007-05-08 11:15:07 -07:00
kfifo.c [PATCH] Numerous fixes to kernel-doc info in source files. 2007-02-11 10:51:32 -08:00
kmod.c wait_for_helper: remove unneeded do_sigaction() 2007-05-09 12:30:53 -07:00
kprobes.c Kprobes: The ON/OFF knob thru debugfs 2007-05-08 11:15:19 -07:00
ksysfs.c remove "struct subsystem" as it is no longer needed 2007-05-02 18:57:59 -07:00
kthread.c mm: fix improper .init-type section references 2007-07-16 09:05:36 -07:00
latency.c [PATCH] severing module.h->sched.h 2006-12-04 02:00:22 -05:00
lockdep.c lockdep: removed unused ip argument in mark_lock & mark_held_locks 2007-05-08 11:15:13 -07:00
lockdep_internals.h [PATCH] lockdep: more chains 2006-12-07 08:39:43 -08:00
lockdep_proc.c [PATCH] remove many unneeded #includes of sched.h 2007-02-14 08:09:54 -08:00
Makefile user namespace: add the framework 2007-07-16 09:05:47 -07:00
module.c Make /proc/modules use seq_list_xxx helpers 2007-07-16 09:05:42 -07:00
mutex-debug.c [PATCH] remove many unneeded #includes of sched.h 2007-02-14 08:09:54 -08:00
mutex-debug.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
mutex.c wrap access to thread_info 2007-05-09 12:30:56 -07:00
mutex.h [PATCH] lockdep: prove mutex locking correctness 2006-07-03 15:27:04 -07:00
nsproxy.c namespace: ensure clone_flags are always stored in an unsigned long 2007-07-16 09:05:48 -07:00
panic.c [PATCH] Add TAINT_USER and ability to set taint flags from userspace 2007-02-11 10:51:29 -08:00
params.c sysfs: kill unnecessary attribute->owner 2007-07-11 16:09:06 -07:00
pid.c namespace: ensure clone_flags are always stored in an unsigned long 2007-07-16 09:05:48 -07:00
posix-cpu-timers.c sched: make posix-cpu-timers use CFS's accounting information 2007-07-09 18:51:58 +02:00
posix-timers.c posix-timers: Prevent softirq starvation by small intervals and SIG_IGN 2007-06-21 15:57:04 -07:00
printk.c add printk.time option, deprecate 'time' 2007-07-16 09:05:45 -07:00
profile.c Detach sched.h from mm.h 2007-05-21 09:18:19 -07:00
ptrace.c Use write_trylock_irqsave in ptrace_attach 2007-07-16 09:05:40 -07:00
rcupdate.c Add suspend-related notifications for CPU hotplug 2007-05-09 12:30:56 -07:00
rcutorture.c rcutorture: Remove redundant assignment to cur_ops in for loop 2007-05-08 11:15:17 -07:00
relay.c relay: fixup kerneldoc comment 2007-07-13 14:14:28 +02:00
resource.c libata/IDE: remove combined mode quirk 2007-04-28 14:15:59 -04:00
rtmutex-debug.c Remove all inclusions of <linux/config.h> 2006-10-04 03:38:54 -04:00
rtmutex-debug.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
rtmutex-tester.c [PATCH] Add include/linux/freezer.h and move definitions from sched.h 2006-12-07 08:39:27 -08:00
rtmutex.c Revert "futex_requeue_pi optimization" 2007-06-18 09:48:41 -07:00
rtmutex.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
rtmutex_common.h Revert "futex_requeue_pi optimization" 2007-06-18 09:48:41 -07:00
rwsem.c Lockdep treats down_write_trylock like regular down_write 2007-05-08 11:15:09 -07:00
sched.c CFS: Fix missing digit off in wmult table 2007-07-13 16:45:43 -07:00
sched_debug.c [PATCH] sched: remove stale version info from kernel/sched_debug.c 2007-07-13 10:10:41 -07:00
sched_fair.c sched: cfs core, kernel/sched_fair.c 2007-07-09 18:51:58 +02:00
sched_idletask.c sched: cfs core, kernel/sched_idletask.c 2007-07-09 18:51:58 +02:00
sched_rt.c sched: cfs core, kernel/sched_rt.c 2007-07-09 18:51:58 +02:00
sched_stats.h sched: update delay-accounting to use CFS's precise stats 2007-07-09 18:52:00 +02:00
seccomp.c
signal.c vdso: print fatal signals 2007-07-16 09:05:43 -07:00
softirq.c cpu hotplug: fix ksoftirqd termination on cpu hotplug with naughty realtime process 2007-07-16 09:05:41 -07:00
softlockup.c Add suspend-related notifications for CPU hotplug 2007-05-09 12:30:56 -07:00
spinlock.c [PATCH] lockdep: spin_lock_irqsave_nested() 2006-11-25 13:28:34 -08:00
srcu.c [PATCH] SRCU: report out-of-memory errors 2006-10-04 07:55:30 -07:00
stacktrace.c [PATCH] lockdep: stacktrace subsystem, core 2006-07-03 15:27:02 -07:00
stop_machine.c Fix stop_machine_run problem with naughty real time process 2007-07-16 09:05:41 -07:00
sys.c user namespace: add the framework 2007-07-16 09:05:47 -07:00
sys_ni.c diskquota: 32bit quota tools on 64bit architectures 2007-07-16 09:05:48 -07:00
sysctl.c vdso: print fatal signals 2007-07-16 09:05:43 -07:00
taskstats.c taskstats: add context-switch counters 2007-07-16 09:05:46 -07:00
time.c sys_time() speedup 2007-07-16 09:05:48 -07:00
timer.c Add a flag to indicate deferrable timers in /proc/timer_stats 2007-07-16 09:05:45 -07:00
tsacct.c [PATCH] time: x86_64: split x86_64/kernel/time.c up 2007-02-16 08:14:00 -08:00
uid16.c header cleaning: don't include smp_lock.h when not used 2007-05-08 11:15:07 -07:00
user.c user namespace: add the framework 2007-07-16 09:05:47 -07:00
user_namespace.c fix create_new_namespaces() return value 2007-07-16 09:05:47 -07:00
utsname.c namespace: ensure clone_flags are always stored in an unsigned long 2007-07-16 09:05:48 -07:00
utsname_sysctl.c remove CONFIG_UTS_NS and CONFIG_IPC_NS 2007-07-16 09:05:47 -07:00
wait.c Fix occurrences of "the the " 2007-05-09 08:57:56 +02:00
workqueue.c simplify cleanup_workqueue_thread() 2007-05-23 20:14:13 -07:00